1. Field of the Invention
The present disclosure relates to a device and a method for reducing fuel dilution of a diesel engine. More particularly, it relates to a device and a method for reducing fuel dilution of a diesel engine, which can prevent an engine oil dilution phenomenon in which fuel is mixed with engine oil in a diesel engine having a diesel particulate filter trap (DPF) mounted therein.
2. Description of Related Art
In general, a diesel engine vehicle discharges particulates, and hence an aftertreatment device is mounted in the diesel engine vehicle in order to reduce the particulates. The representatives of the aftertreatment device are a diesel particulate filter trap (DPF), a diesel oxidation catalyst (DOC), and the like.
The DPF is a particulate material reduction technique that is currently most efficient and approaches commercialization. The particulate material reduction technique is a technique of collecting particulates discharged from a diesel engine using a DPF filter and then burning (regenerating) the collected particulates, and again collecting particulates to be continuously used. The DPF can reduce particulates up to 80% or more, which has a very excellent advantage in terms of its performance. However, the durability and economy of the DPF act as obstacles against commercialization.
As particulates are collected in the DPF filter, a back-pressure is applied to the engine, and the output and fuel consumption rate of the engine is slightly decreased by the back-pressure. Therefore, it is required to complement a technique for minimizing this.
The DPF technique is generally divided into a PM collection technique and a filter regeneration technique. The DPF technique is basically configured with three parts, i.e., a filter, a regeneration device and a control device.
In order to regenerate the DPF, it is important to increase exhaust temperature up to 650 that is a DPF activation temperature. Accordingly, the DPF activation temperature can be maintained through post injection in which the fuel injection in a combustion chamber is performed after top dead center (ATDC). The ATDC is to delay ignition delay time, and means before and after top dead center (to close intake and exhaust valves before and after top dead center).
In order to regenerate the DPF, it is important to start DPF regeneration by increasing the temperature of the DPF up to the DPF activation temperature. As a plan for always maintaining a constant temperature during the regeneration of the DPF, an oxidation reaction occurs inside the DPF through the post injection.
Meanwhile, if fuel is injected at the time when a piston of the engine descends toward a bottom dead center, the injected fuel flows up to the inside of the DPF through the exhaust valve. Therefore, an engine oil dilution phenomenon occurs in which, when the piston descends toward the bottom dead center except the purpose of maintaining the DPF activation temperature, the injected fuel that exists on the wall surface of a cylinder in a non-combustion state is naturally mixed with engine oil through a piston ring.
If the engine oil is returned to an oil pan by circulation of the engine oil in the state in which the fuel is diluted by the engine oil, the fuel exists in the oil pan while being diluted by the engine oil.
In the current manner that the DPF is regenerated through the post injection, the engine oil dilution phenomenon has bad influence on cooling of various engine components and lubricant. In addition, a dieseling phenomenon is caused in which the engine oil is flowed in the combustion chamber and then burnt. As a result, there is a problem in that the durability of the engine is deteriorated.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.